This invention relates to an optical fiber splice for coupling fibers together.
When placing optical fibers in end-to-end relationship to minimize light loss, it is desirable to have a rugged splice that can be simply and reliably used in field installations. The fibers at the junction should be firmly held to prevent the fibers from moving apart at the junction.
U.S. Pat. No. 4,257,674 (Griffin et al) describes a splice for holding the ends of optical fibers in end-to-end relationship. The splice mechanism includes a pair of sections having mating planar surfaces. One of the surfaces has an axially aligned groove facing the other surface to form a triangular section passage. The sections are formed of an elastomeric material of sufficient resilience to receive an optical fiber of marginally greater diameter than that defined by the passage. A sleeve is mounted about the elastomeric sections to hold them in assembled relationship.
To use the splice device the ends of fibers to be joined are cleaved and stripped of jacket material. One of the fibers is inserted into the triangular passage defined by the groove and facing surface until it extends approximately to midway through the passage. The other fiber is then inserted from the other end until it abuts the end of the first fiber. Because the triangular passage is undersized in comparison to the stripped fiber, a force fit results which acts both to render the fibers substantially coaxial and to grip the fibers so as to prevent axial separation. A problem with such mechanical splices is that the force acting laterally on the fibers must be great enough to centralize the two fibers. On the other hand, if that force is to be high it means that a fiber is subjected to great frictional resistance as it is inserted into the triangular passage. Consequently, it is difficult for a user on inserting the second fiber to feel when the fiber abuts the first-inserted fiber.
U.S. Pat. No. 3,734,594 (Trambaruio) describes a similar splice. A hollow elastomer cylinder having a bore marginally greater in diameter than fibers to be joined has annular bearing surfaces at respective ends. Fibers are inserted into the bore from both ends and then the bearing surfaces are pushed towards one another. As the elastomer material is squeezed from the ends, it expands in the middle and in doing so grips the fibers and acts to coaxially align them. Ideally, on compressing the elastomer from its ends the inner surface of the elastomer moves a small and uniform distance radially inwardly. In fact, owing to non-uniformity in elasticity of a typical elastomer block the radial movement is not uniform and this can lead to microbending of the fibers gripped by the splice with consequent splice loss.